1. Field of the Invention
The present invention relates to an apparatus for manufacturing an LCD device, and more particularly, to an ink-jet printing apparatus which coats an alignment layer or the like on an LCD device.
2. Discussion of the Related Art
Ultra-thin flat type display devices have many applications. These display devices include a display screen having a thickness of several centimeters. Among the ultra-thin flat type display panels, liquid crystal display (LCD) devices have been used in a number of applications, including notebook computers, monitors, spacecraft, aircraft, etc.
Generally, a LCD device has a lower substrate, an upper substrate, and a liquid crystal layer formed in a gap between the lower substrate and the upper substrate. Typically, when a voltage is applied, the alignment of the liquid crystal layer changes. Thus, driving the liquid crystal layer controls light transmittance of the LCD device, thereby displaying images.
However, if the arrangement of the liquid crystal molecules becomes disordered when the voltage is applied, it is impossible to obtain a desired image. Thus, alignment layers should be formed on the lower and upper substrates in order to initially align the liquid crystal layer.
Generally, a method for forming the alignment layer is classified into a rubbing alignment method or a photo alignment method.
In the rubbing alignment method, an alignment material is thinly coated on a substrate. After coating, a rubbing roll having a rubbing cloth wound thereon rolls on the coated alignment material.
In the photo alignment method, an alignment material is thinly coated on a substrate. After coating, a polarized or non-polarized UV ray is applied to the coated alignment material.
The alignment material should be uniformly coated on the substrate such that the alignment layer is arranged in one direction when applying either the rubbing alignment method or the photo alignment method.
Hereinafter, a related art method for coating an alignment material on a substrate will be described with reference to the accompanying drawings.
FIG. 1 is a cross sectional view showing a method for coating an alignment layer with a related art roll printing apparatus.
The related art roll printing apparatus is provided with a substrate stage 12 for supporting a substrate 10, a dispenser 14 for supplying an alignment material, a doctor roll 16, an anilox roll 18, and a printing roll 20. The doctor roll 16 engages with the anilox roll 18 and the anilox roll 18 engages with the printing roll 20.
The printing roll 20 has a rubber plate 22 attached thereto suitable for printing a desired pattern of the alignment material.
A method for coating the alignment layer with the above roll printing apparatus will be described as follows. First, the alignment material 15 of the dispenser 14 is supplied between the doctor roll 16 and the anilox roll 18. In this case, because the doctor roll 16, the anilox roll 18, and the printing roll 20 are engaged with one another, and revolve as indicated by the directional arrows, the alignment material 15, supplied between the doctor roll 16 and the anilox roll 18, is uniformly coated on the rubber plate 22 on the printing roll 20 through the anilox roll 18.
In the meantime, the substrate 10 is placed on the substrate stage 12, and the substrate stage 12 moves in a predetermined direction below the printing roll 20. When the substrate stage 12 moves, the substrate 10 placed on the substrate stage 12 contacts the rubber plate 22 of the printing roll 20. Thus, the alignment material coated on the rubber plate 22 is printed on the substrate 10, whereby the alignment material is coated on the substrate 10.
However, the method for coating the alignment material with the roll printing apparatus according to the related art has the following disadvantages.
First, the sizes of the three rolls must be changed when a model size of the LCD device changes. Second, for applications having a larger substrate which require a larger printing roll, it becomes more difficult to evenly coat alignment material on the entire surface of the substrate. Third, use of the printing roll device wastes a fair amount of alignment material, thereby increasing production costs associated with coating a substrate using the related art roll printing apparatus.